1. Technical Field
This invention relates to sheet inverting mechanisms for use in sheet handling equipment, and more particularly to such a sheet mechanism that has dual drive assemblies for quickly reversing the direction of movement of a sheet in a sheet handling equipment such as a high-speed copier or printer.
2. Background Art
As disclosed, for example, in U.S. Pat. Nos. 4,847,506, issued Dec. 11, 1984 to Repp et al; U.S. Pat. No. 5,082,272, issued Jan. 21, 1992 to Xydias et al; and U.S. Pat. No. 5,131,649, issued Jul. 21, 1992 to Martin et al, sheet inverting mechanisms, such as J-turnover devices, are well known for use in electrostatographic copiers and printers. Such sheet inverting mechanisms are used to reverse the lead and trail edges, and hence the front-and-back face orientation of a sheet being handled in such a copier or printer.
Typically, each such sheet inverting mechanism includes a sheet containment chamber that has a first end with a sheet input nip for feeding sheets into the chamber and with an output nip for reversibly feeding sheets out of the chamber. The chamber also has a second end with a reversible sheet driving assembly for moving sheets within the chamber first in a forward direction and then reversibly in the opposite direction. As disclosed, for example in the U.S. Pat. No. 5,082,272 patent, such a reversible sheet driving assembly can be a passive spring, but as disclosed in the U.S. Pat. No. 4,487,506 patent, it can also be a reversible drive motor that is connected to sheet moving rollers by means of a pair of reversible meshing gears which rotate first in one direction, and then reversibly in an opposite direction.
Alternatively, the reversible sheet driving assembly can be a reversible roller drive assembly that is mounted on a movable support that shifts first to one side to drive sheet moving rollers in one direction, and then to a second and opposite side to drive the sheet moving rollers in an opposite direction. As can be expected in such conventional reversible sheet driving assemblies, motion in a first direction along with the attendant inertia of all moving components must first be brought to a complete stop before motion in a second and opposite direction can be started. This aspect of such assemblies can be a drawback.
In high-speed sheet handling equipment, and particularly in a sheet inverting mechanism for moving two sheets simultaneously as well as in opposite directions within the containment chamber, such conventional drive assemblies are slow, and are very likely to result in bottlenecks, sheet wrinkling and maybe jams when used in high-speed copiers or printers.